For this case, assume that the requesting host is on class B network 128.99.0.0, has address 128.99.4.123, that there is a gateway at 128.99.4.62, and that a 6-bit wide subnet field is in use, that is, the address mask is 255.255.252.0.
The host sends the ICMP request to 255.255.255.255:
Source address: 128.99.4.123 Destination address: 255.255.255.255 Protocol: ICMP = 1 Type: Address Mask Request = AM1 Code: 0 Mask: 0The gateway can then respond directly to the requesting host.
Source address: 128.99.4.62 Destination address: 128.99.4.123 Protocol: ICMP = 1 Type: Address Mask Reply = AM2 Code: 0 Mask: 255.255.252.0In the diskless workstation case the host sends:
Source address: 0.0.0.0 Destination address: 255.255.255.255 Protocol: ICMP = 1 Type: Address Mask Request = AM1 Code: 0 Mask: 0128.99.4.62 will hear the datagram, and should respond with this datagram:
Source address: 128.99.4.62 Destination address: 255.255.255.255 Protocol: ICMP = 1 Type: Address Mask Reply = AM2 Code: 0 Mask: 255.255.252.0If broadcasting is not allowed 128.99.4.123 sends:
Source address: 128.99.4.123 Destination address: 128.99.4.62 Protocol: ICMP = 1 Type: Address Mask Request = AM1 Code: 0 Mask: 0128.99.4.62 should respond exactly as in the previous case.
Source address: 128.99.4.62 Destination address: 128.99.4.123 Protocol: ICMP = 1 Type: Address Mask Reply = AM2 Code: 0 Mask: 255.255.252.0